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• Introduction to R - due date: 22 Jan 2021 23:59
• Intermediate R - due date: 22 Jan 2021 23:59

Homework I & II and Midterm Project

• HMW - I - due date: 22 Dec 2020 23:59
• HMW - II - due date: 22 Dec 2020 23:59
• Midterm Project - due date: 18 Dec 2020 23:59

Questions - R Language

• What are the benefits of R-Script and R-Project?
• What are the data types and data structures in R?
• What are the advantages of the Data Frame?
• What is the difference between NA and NaN?

What is Function ?

A function is a set of statements organized together to perform a specific task

ex: mean() (arithmetic mean)

x <- c(1,2,3)
mean(x)

## [1] 2

(1+2+3) / 3

## [1] 2

Create a Function

Create a Function

Create a Function

Problem: Take a sample belonged to population, and sum

box <- 1:6                    # This is my population in a BOX
box

## [1] 1 2 3 4 5 6

samp <- sample(box, size = 2)   # This is my sample, I choose two values.
samp

## [1] 3 1

sum(samp)

## [1] 4

Create a Function

I want to collect my sample() and sum() functions and put in ONE function. I will create a new function named roll2().

name_new_function <- function( argument ) {

name_new_variable <- do_this( argument, option )
then_do_this( name_new_variable )
}

name_new_function( )    # It will work with my default argument

Create a Function

name_new_function <- function( argument ) {

name_new_variable <- do_this( argument, option )
then_do_this( name_new_variable )
}

name_new_function( )   # It will work with my default argument

in formal :

roll2 <- function(box = 1:6) {
  
samp <- sample(box, size=2) 
sum(samp)
}

roll2( )      # It will work with my default argument ( box = 1:6 )

## [1] 10

Create a Function

roll2 <- function(box = 1:6) {
  
samp <- sample(box, size=2) 
sum(samp)
}

roll2()    # It will work with my default argument ( box = 1:6 )

## [1] 7

Create a Function

You can change the default argument in every time

roll2(box = 1:10)   # It will work with argument ( 1,2,3,4,5,6,7,8,9,10 )

## [1] 11

roll2(1:10)   # It will work with argument ( 1,2,3,4,5,6,7,8,9,10 )

## [1] 18

roll2(seq(1,10,0.5))   # It will work with argument ( 1, 1.5, 2, 2.5, 3,... )

## [1] 9.5

Practice - Create a Function

You can add new options or new functions in your new function.

{ } and () are important

# Think about these functions
# mean(), print(), plot(), max(), install.packages(), help(), ...

R Programming - Conditions

TRUE & TRUE  
TRUE & FALSE
TRUE | FALSE 
!TRUE

2 == 3
5 < 6

c(1,4) >= 6

9 != 8

5 < 6 & 9 != 8

score <- 80
exam_name <- "math"

score >= 75 & exam_name == "math"

if (Stand-Alone) Statement

The if statement executes a chunk of code if and only if a defined condition is TRUE, which looks something like this:

if(TRUE) message("It was true!")

## It was true!

if(FALSE) message("It wasn't true!")

if(TRUE&FALSE) message("It was true!")

if(TRUE|FALSE) message("It doesn't matter")

## It doesn't matter

if (Stand-Alone) Statement

a <- 3
num <- 4

if ( a != num ) {
print(a)
}

## [1] 3

a <- 3
num <- 4

if ( a <= num ) {
a <- a ^ 2
print(a)
}

## [1] 9

if (Stand-Alone) Statement

num <- -1

if ( num < 0 ) {
  print("num is negative.")
  print("Don't worry, I'll fix it.") 
  num <- num * -1
  print(num)
  print("Now num is positive.")
}

## [1] "num is negative."
## [1] "Don't worry, I'll fix it."
## [1] 1
## [1] "Now num is positive."

if (Stand-Alone) Statement

just look

if (Stand-Alone) Statement

just look

if (Stand-Alone) Statement

Try it

Is it in the range ?

x <- 6
y <- 2

if ( x > 3 & x == 7 ) {
  print("It is in the range")
  z <- x + y
  print(z)
}

Can you fix this, with just ONE symbol ?

if (Stand-Alone) Statement

Is it in the range ?

x <- 6
y <- 2

if ( x > 3 & x <= 7 ) {
  print("It is in the range")
  z <- x + y
  print(z)
}

## [1] "It is in the range"
## [1] 8

if (Stand-Alone) Statement

Try it

You have a fruit which is yellow.

Is that a banana?

Or an orange ?

banana <- "yellow"
my_fruit <- "yellow"

if ( my_fruit == banana ) {
  print("Your fruit might be a banana")
}

orange <- "orange"
my_fruit <- "yellow"

if ( my_fruit == orange ) {
  print("Your fruit is not a banana")
}

else - Statement

If you want something different to happen when the condition is FALSE, you can add an else declaration.

if(FALSE) {
      message("This won't appearance ...")
} else {
      message("but this will !")
}

## but this will !

a <- 3.5
b <- 0.5

if (a <= 0.5) {
  c <- b + 1
  print(c)
} else {
  c <- b
  print(c)
}

## [1] 0.5

else - Statement

Report the weather. Is it rainy ?

Let’s say we have two conditions. Rainy or Shiny.

And you have recorded 4 mm precipitation.

weather <-       # mm           # fill this number

if ( ) {                        # fill this condition, using weather
  print("it is rainy")
} else {
  print("it is shiny")
}

else - Statement

Report the weather. Is it rainy ?

Let’s say we have two conditions. Rainy or Shiny.

And you have recorded 4 mm precipitation.

weather <- 4      # mm              # fill this number

if ( weather > 0 ) {                # fill this condition, using weather
  print("it is rainy")              
} else {
  print("it is shiny")
}

## [1] "it is rainy"

-else - and -else if- Statement

If your situation has more than two mutually exclusive cases, use else and if statements together.

-else - and -else if- Statement

If your situation has more than two mutually exclusive cases, use else and if statements together.

a <- 1                  # team 'a' has 1 goal
b <- 1                  # team 'b' has 1 goal

if (a > b) { 
  print("A wins!")
} else if (a < b) { 
  print("B wins!")
} else {
  print("Tie.")
}

## [1] "Tie."

-else - and -else if- Statement

What do you gonna do ? Eating, Sleeping, or Reading?

When do you want to read ?

• When you are hungry, or sleepy. No.
• When you are not hungry and sleepy. Yes.

So, start to think about your feelings about sleeping or eating to decide whether reading or not.

-else - and -else if- Statement

What do you gonna do ? Eating, Sleeping, or Reading?

Let’s start with define the conditions

• If you are hungry –> eat

• If you are sleepy –> sleep

  • If you are hungry and sleepy –> ?
  • If you are hungry but not sleepy –> ?
  • If you are not hungry but sleepy –> ?
  • If you are not hungry and sleepy –> ?

-else - and -else if- Statement

What do you gonna do ? Eat, Sleep or Read?

• If you are hungry and sleepy –> eat
• If you are hungry but not sleepy –> eat
• If you are not hungry but sleepy –> sleep
• If you are not hungry and sleepy –> read

Let’s define your feelings. Yes (TRUE,1) or No (FALSE,0)

• Are you hungry ?
• Are you sleepy ?

hungry <-                   # TRUE or FALSE (1 or 0)
sleepy <-                   # TRUE or FALSE (1 or 0)

-else - and -else if- Statement

What do you gonna do ? Eat, Sleep or Read?

• 1. If you are hungry and sleepy –> eat
• 2. If you are hungry but not sleepy –> eat
• 3. If you are not hungry but sleepy –> sleep
• 4. If you are not hungry and sleepy –> read

hungry <- TRUE                  # Yes , TRUE , 1
sleepy <- TRUE                  # Yes , TRUE , 1

if ( ) { 
  print(" ")
} else if ( ) { 
  print(" ")
} else if ( ) { 
  print(" ")
} else {
  print(" ")
}

-else - and -else if- Statement

What do you gonna do ? Eat, Sleep or Read?

• 1. If you are hungry and sleepy –> eat
• 2. If you are hungry but not sleepy –> eat
• 3. If you are not hungry but sleepy –> sleep
• 4. If you are not hungry and sleepy –> read

hungry <- TRUE                  # Yes , TRUE , 1
sleepy <- TRUE                  # Yes , TRUE , 1

if ( ) {                    # hungry is TRUE and sleepy is TRUE
  print(" ")
} else if ( ) {             # hungry is TRUE and sleepy is FALSE
  print(" ")
} else if ( ) {             # hungry is FALSE and sleepy is TRUE
  print(" ") 
} else {                    # hungry is FALSE and sleepy is FALSE
  print(" ")
}

-else - and -else if- Statement

What do you gonna do ? Eat, Sleep or Read?

• If you are hungry and sleepy –> eat
• If you are hungry but not sleepy –> eat
• If you are not hungry but sleepy –> sleep
• If you are not hungry and sleepy –> read

hungry <- TRUE                  # Yes , TRUE , 1
sleepy <- TRUE                  # Yes , TRUE , 1

if (hungry==TRUE & sleepy==TRUE) {          # hungry is TRUE and sleepy is TRUE
  print(" ")
} else if (hungry==TRUE & sleepy==FALSE) {  # hungry is TRUE and sleepy is FALSE
  print(" ")
} else if (hungry==FALSE & sleepy==TRUE) {  # hungry is FALSE and sleepy is TRUE
  print(" ") 
} else {                                    # hungry is FALSE and sleepy is FALSE
  print(" ")
}

## [1] " "

-else - and -else if- Statement

What do you gonna do ? Eat, Sleep or Read?

• If you are hungry and sleepy –> eat
• If you are hungry but not sleepy –> eat
• If you are not hungry but sleepy –> sleep
• If you are not hungry and sleepy –> read

hungry <- TRUE                  # Yes , TRUE , 1
sleepy <- TRUE                  # Yes , TRUE , 1

if (hungry==TRUE & sleepy==TRUE) {          # hungry is TRUE and sleepy is TRUE
  print("EAT")
} else if (hungry==TRUE & sleepy==FALSE) {  # hungry is TRUE and sleepy is FALSE
  print("EAT")
} else if (hungry==FALSE & sleepy==TRUE) {  # hungry is FALSE and sleepy is TRUE
  print("SLEEP") 
} else {                                    # hungry is FALSE and sleepy is FALSE
  print("READ")
}

## [1] "EAT"

Nesting and Stacking Statements

An if statement can be placed in another if statement. In the editor, modify the mynumber example once more as follows:

Nesting and Stacking Statements

Nesting and Stacking Statements

Nesting and Stacking Statements

Nesting and Stacking Statements

Practice - Conditions - TRUE and FALSE

1. Print this if it is TRUE. “This message will print!”

if (...) {
  print(...)
} 

2. Go to bed if time equals to 22 o’clock, else wake up.

if (...) {
   print("Go to bed!")
} else {
   print("Wake up!")
}

3. The variable message to “I print this when it is false!” when the condition is FALSE.

if (...) {
  print("I print this when it is true!")
} else {
  print(...)
}

Practice - Conditions - Logical Op

ROLE PLAY : You are a CAR, and you are going on the road.

Problem : BUT ;

• Traffic (stop) light turned to orange
• Two pedestrians started to walk across the road

How can you move ?

Practice - Conditions - Logical Op

How can you move ?

• Waiting for the traffic (stop) light turns to green
• Waiting for pedestrians pass to the across of the road

Parameters :

Practice - Conditions - Logical Op

How can you move ?

• Waiting for the traffic (stop) light turns to green
• Waiting for pedestrians pass to the across of the road

Parameters :

• The COLOR of the traffic (stop) light
• The NUMBER of pedestrians

Practice - Conditions - Logical Op

You are a CAR, BUT ;

• Traffic (stop) light turned to orange
• Two pedestrians started to walk across the road

Parameters :

• The COLOR of the traffic (stop) light
• The NUMBER of pedestrians

First, define the situation

Traffic_Stop_Light <- 
Number_of_Pedestrians <-

Practice - Conditions - Logical Op

You are a CAR, BUT ;

• Traffic (stop) light turned to orange
• Two pedestrians started to walk across the road

Parameters :

• The COLOR of the traffic (stop) light
• The NUMBER of pedestrians

First, define the situation

Traffic_Stop_Light <- 'orange'
Number_of_Pedestrians <- 2

Practice - Conditions - Logical Op

You are a CAR, BUT ;

Traffic_Stop_Light <- 'orange'
Number_of_Pedestrians <- 2

Second, define the conditions to move again

Traffic_Stop_Light : ?
Number_of_Pedestrians : ?

Practice - Conditions - Logical Op

Situation

Traffic_Stop_Light <- 'orange'
Number_of_Pedestrians <- 2

Condition

Traffic_Stop_Light : 'green'
Number_of_Pedestrians : 0

Remember rules

if (...) {
  print(...);
} else {
  print(...);
}

Practice - Conditions - Logical Op

Situation

Traffic_Stop_Light <- 'orange'
Number_of_Pedestrians <- 2

Condition

Traffic_Stop_Light : 'green'
Number_of_Pedestrians : 0

Remember rules

if ( & ) {
  print('Go!');
} else {
  print('STOP');
}

Practice - Conditions - Logical Op

Situation

Traffic_Stop_Light <- 'orange'
Number_of_Pedestrians <- 2

Condition

Traffic_Stop_Light : 'green'
Number_of_Pedestrians : 0

Remember rules

if (Traffic_Stop_Light=='green' & Number_of_Pedestrians==0) {
  print('Go!');
} else {
  print('STOP');
}

## [1] "STOP"

Practice - Conditions - Logical Op

Problem : You want to enjoy at the weekend (“Saturday” or “Sunday”), and let’s say the day is;

day <- "Friday"

What do you gonna do if it is Friday.

if (...) {
  print('Enjoy the weekend!')
} else {
  print('Do some work.')
}

Practice - Conditions - Logical Op

Problem : You want to enjoy at the weekend (“Saturday” or “Sunday”), and let’s say the day is;

day <- "Friday"

What do you gonna do if it is Friday.

if ( day... | day... ) {
  print('Enjoy the weekend!')
} else {
  print('Do some work.')
}

Practice - Conditions - Logical Op

ANSWER : You want to enjoy, and let’s say the day is;

day <- "Friday"

It is okay, you can fun if it is weekend.

if (day == 'Saturday' | day == 'Sunday') {
  print('Enjoy the weekend!')
} else {
  print('Do some work.')
}

## [1] "Do some work."

Practice - Conditions - Logical Op

Problem : You want to go out and your question is

“Should I take an umbrella?”

Note : There are two variables in your code,

“sky” (character) and “high_chance_of_rain” (logical)

• Check, if “sky” is equal to “cloudy” and, whether there is a “high_chance_of_rain”.

• If both are true, the code should print: “Take umbrella!”

• Otherwise, the code should print: “No need for umbrella!”

• Based on the condition, what is the answer?

    RADIO: The sky is cloudy and the chance of rain is high.

Practice - Conditions - Logical Op

Your conditions, for two variables

# you want to go out and your question is "Should I take an umbrella?"

sky <- 

high_chance_of_rain <- 

Practice - Conditions - Logical Op

Your conditions, for two variables

# you want to go out and your question is "Should I take an umbrella?"

sky <- "cloudy"

high_chance_of_rain <- TRUE

Practice - Conditions - Logical Op

# you want to go out and your question is "Should I take an umbrella?"

sky <- "cloudy"

high_chance_of_rain <- TRUE

if (...) {
  print("...")
} else { 
  print("...")
  }

Practice - Conditions - Logical Op

# you want to go out and your question is "Should I take an umbrella?"

sky <- "cloudy"

high_chance_of_rain <- TRUE

if (...) {
  print("Take umbrella!")
} else { 
  print("No need for umbrella!")
  }

Practice - Conditions - Logical Op

# you want to go out and your question is "Should I take an umbrella?"

sky <- "cloudy"

high_chance_of_rain <- TRUE

if ( sky... & high_chance_of_rain... ) {
  print("Take umbrella!")
} else { 
  print("No need for umbrella!")
  }

Practice - Conditions - Logical Op

# you want to go out and your question is "Should I take an umbrella?"

sky <- "cloudy"

high_chance_of_rain <- TRUE

if (sky == "cloudy" & high_chance_of_rain == TRUE) {
  print("Take umbrella!")
} else { 
  print("No need for umbrella!")
  }

## [1] "Take umbrella!"

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R Programming - Part - I & II

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